What do Eurasian watermilfoil, Didymo, water chestnut, purple loosestrife, fishhook water fleas, zebra mussels, and round gobies have in common? They are all species from other parts of the world that have been accidentally introduced and have flourished in New York State, oftentimes at the expense of valuable natived to water which they were not originally found. These plants and animals are all considered invasive species and, when they become problems, are termed nuisance invasive species. Without the predators, parasites and diseases that control their numbers in their native habitats, these species can reproduce and spread at an amazing pace. Similarly, fish diseases such as whirling disease and viral hemorrhagic septicemia (VHS) have also been introduced to New York State. Although these diseases are not a threat to human health, they can have dire consequences for our native fish communities.